Combined antitank gun and mortar

[fortrena]

Would anyone have information on this late 30s or early 40s weapon prototype, which combined a 37 mm Bofors antitank gun and a breech loaded 81 mm (Bofors?) mortar?

The combined weapon weighed approximatelky 450 kg.

Incidentally, the mortar could apparently fire a 4.1 kg projectile to a distance of up to 6 000 m, which was pretty good for the time given that the M1 mortar of the U.S. Army seemingly fired a 3.1 kg projectile to a distance of a tad more than 3 000 m.

 

[Nik]

Um, how long to lower from 'support' mortar / sorta-howitzer setting to 'F**kitsaTank' ??

 

[eltf177]

Reminds me a bit of the Japanese Type 92 70mm Battalion Gun introduced in 1932. Capable of direct fire or up to 70o elevation for use as a howitzer/mortar. Also had a hollow-charge AT round giving it substantial AT capability.

 

[Nik]

Tangential, IIRC, the 'Alpine Campaigns' during WW1, besides killing many more from hypothermia & avalanches than direct gunfire, needed hasty re-working of ballistics charts. Mountain air was sufficiently colder, dryer and thinner to throw-off both ammunition performance and aiming. Aggravated by oft-howling mountain & valley winds, often different directions at different altitudes. Worse, IIRC, existing charts did not adequately account for the very high angles for oft-considerable altitude differences and/or scary-short ranges. The possibility of being 'hoist by your own petard' could be very real...

Thick snow-pack is a remarkably effective swallower of blast & shrapnel, so opposing positions could be within shouting distance, yet no effective weapon brought to bear...

Which is why, IIRC, both sides took to attacking overhanging crest cornices etc etc. An overnight wind-shift could briskly emplace such a 'Sword of Damocles' above a stubborn enemy position or persistent re-supply route. So, gotta drop their cornice on them before they drop your cornice on you...

I suppose supreme irony is that H, who'd apparently lost enough kith+kin in the Alps to deter him from grabbing Switzerland, instead lost entire armies to the Russian Winter...

 

[World B4]

... I've never seen a combination gun that's also artillery before

 

[TomS]

Pedantically, mortars aren't artillery. But I guess AT guns are...

Superficially, this thing looks like it ought to make sense as a way to replace both infantry AT guns and mortars with a single asset. But I'd expect that an infantry unit on the defense especially would want to be able to employ both mortars and AT guns simultaneously. And the right location for one is the wrong place for the other, tactically.

 

[Stranger_NN]

+ Thailand/Siam Type 77. 1935 (2577 according to the Thai calendar) Bofors 47/75 dual caliber gun. Тotal of 30 (maybe 40-42?) guns were made.

 

[Stranger_NN]

Chinese Bofors 37/81 dual gun. 1933. Тotal of 12 guns were made.

 

[Stranger_NN]

Skoda BA-1/AB-1 37/70-mm gun. 1932. Czechoslovakia for China. One prototype was built.
Skoda Pilsen took advantage of the difference in calibers and developed a system that simply inserted a small caliber barrel into a larger barrel, a 18 kg 37 mm barrel was inserted into a 70 mm barrel.

 

[Stranger_NN]

I also have to mention Vickers 44/60 and 25/70 combined guns, Rheinmetall HIH-Siderius 37/65 and a few more - but I don’t have normal photos on them. ‍

 

[Stranger_NN]

Oh yes, about the parameters of the Swedish-Chinese 37/81-mm gun, which started the topic:

	37-mm​	81-mm​
Barrel length	L45​	L20
Muzzle velocity (m/s)	800	320
Projectile weight (kg)	0.7	4.4
Maximum firing range (km)	7.1	6
Traverse	±25°	±25°
Elevation	-8°....+80°	-8°....+80°
Gun weight (kg)	450	450
Breech	Horizontal wedge breech	Horizontal wedge breech

 

[riggerrob]

Pedantically, mortars aren't artillery. But I guess AT guns are...

Superficially, this thing looks like it ought to make sense as a way to replace both infantry AT guns and mortars with a single asset. But I'd expect that an infantry unit on the defense especially would want to be able to employ both mortars and AT guns simultaneously. And the right location for one is the wrong place for the other, tactically.

Anti-tank guns need to be line-of-sight.
OTOH mortars prefer to fire from the back side of a small hill. That puts them out of sight from rifles, tank guns, etc.

 

[BB1984]

Pedantically, mortars aren't artillery. But I guess AT guns are...

Superficially, this thing looks like it ought to make sense as a way to replace both infantry AT guns and mortars with a single asset. But I'd expect that an infantry unit on the defense especially would want to be able to employ both mortars and AT guns simultaneously. And the right location for one is the wrong place for the other, tactically.

Anti-tank guns need to be line-of-sight.
OTOH mortars prefer to fire from the back side of a small hill. That puts them out of sight from rifles, tank guns, etc.

Very true, especially in the defense. Still, I think there may be some overlap in mortar vs. ATG emplacement, especially in the 30s and 40s when radios at lower levels were rare to non-existent (the US in the WWII maybe being an exception). My understanding is that a great deal of WWII mortar work was done with either the mortars themselves, or someone very near the mortars, having line of sight to the target. The heavier the mortar, the less this might have been true but 81mm is more "up front" and less artillery like than a 120mm or 4.2" is going to be.

In the defense you could lay wire and still use mortars just as you said, but on the advance not so much. Mortars with troops on the move (advancing, retreating, whatever) would be used more or less as infantry gun replacements/supplements, so moved/sited similarly. Even in the defense, anti-tank guns were best employed from hides and from the flanks, so behind hills, taking advantage of even small defilades, etc. so again, maybe more commonality of positioning.

All that said, clearly the world's militaries collectively decided dual guns weren't worth pursuing beyond a few oddball projects, so maybe positioning is more of an issue than I think and/or a mix of 81mm mortars with a smaller number of dedicated anti-tank guns was seen as far cheaper, plus easier to train.

 

[riggerrob]

By mid-World War 2, any anti-tank smaller than 85 mm was too small to kill tanks. Furthermore, that 85 mm gun needed a long barrel to produce muzzle velocities approaching 3,000 feet per second (900 meters per second) and it really helped if ammo contained a slender penetrating rod (armor piercing fin stabilized discarding sabot). Any anti-tank gun that powerful was far too long and far too heavy to be moved on foot or by Jeep. It needed a heavy-duty artillery tractor.

 

[BB1984]

By mid-World War 2, any anti-tank smaller than 85 mm was too small to kill tanks. Furthermore, that 85 mm gun needed a long barrel to produce muzzle velocities approaching 3,000 feet per second (900 meters per second) and it really helped if ammo contained a slender penetrating rod (armor piercing fin stabilized discarding sabot). Any anti-tank gun that powerful was far too long and far too heavy to be moved on foot or by Jeep. It needed a heavy-duty artillery tractor.

I agree that size killed the traditional anti-tank gun. Even the 50/57mm generation was a handful for crews and by the 75mm generation (Pak40, 17lbr, M5) serious artillery tractors (often semi-tracked) were required. The 88mm Pak43 and Russian 100mm 1944 were probably the practical upper limit, but from 75mm on up the guns were difficult to emplace and impossible to displace under fire, leading to "win or die" engagements, plus the combination of a gun and a semi-tracked prime mover started to get closer to the cost of a tank destroyer or assault gun, both of which were far more effective and versatile.

The bulk and cost of the late war antitank guns, especially the stillborn 128mm / 32lbr guns, was one of the big drivers in the emerging recoilless and high-low pressure solutions (using HEAT) that eventually replaced conventional ATG in the west and did most, but not all, of the old ATG work for the Soviets. These weapons restored the advantages of light weight and small prime movers that were lost to antitank guns.

I will quibble with your timing: APFSDS is relatively recent; only the UK got workable APDS in service in WWII, though APCR was common (HVAP in the US) and the taper bore guns were around; APFSDS wasn't a factor until the T-62 was introduced. Mid-war, maybe 1943, the 75mm generation was in full swing: the 17lbr and M5 were new and the Pak40 had only made it to the front in the previous year. Given anti-tank weapons love of flank shots and the relatively small numbers of heavy tanks, the 75mm generation retained a lot of potency even into 1945.

The first thing in the 85mm / 3000fps class was the Pak43, which the Germans were just introducing in 1943 and which was a fierce weapon even in '45 with plain old AP ammo against anything except maybe the King Tiger and JS-2. The US and UK finished out the war with their 75mm/17 pounders as "good enough", though the 75mm was past its prime (the 17lbr was more powerful to start with and had the advantage of APDS, so remained a good choice).

 

[cluttonfred]

There is also the long-established series of Brandt 60 mm gun-mortars used on Panhard AML armored cars. The later AML 60-20 Serval had an improved long-range mortar that could fire a fairly effective HEAT round (~200 mm penetration) in addition to a 20 mm autocannon and a rifle-caliber machine gun.



Image source: https://www.tanks-encyclopedia.com/coldwar/France/Panhard_AML.php

 

[BB1984]

There is also the long-established series of Brandt 60 mm gun-mortars used on Panhard AML armored cars. The later AML 60-20 Serval had an improved long-range mortar that could fire a fairly effective HEAT round (~200 mm penetration) in addition to a 20 mm autocannon and a rifle-caliber machine gun.

View attachment 675616

Image source: https://www.tanks-encyclopedia.com/coldwar/France/Panhard_AML.php

Brandt did interesting work with 60mm, and later 81mm gun-mortars. The US Coast Guard also used a dual .50/81mm mount on patrol boats that allowed firing down to nearly horizontal during the Vietnam era.

Arguably it's the Russians who really ran with Brandt's idea, producing the NONA series of self propelled 120mm mortars and towed 2B16 NONA-K, though there's also AMOS/NEMO.

An edge case is the PAW 600 high-low pressure gun, which was an anti-tank gun firing modified 81mm mortar bombs.

 

[A Tentative Fleet Plan]

There is also the long-established series of Brandt 60 mm gun-mortars used on Panhard AML armored cars. The later AML 60-20 Serval had an improved long-range mortar that could fire a fairly effective HEAT round (~200 mm penetration) in addition to a 20 mm autocannon and a rifle-caliber machine gun.

View attachment 675616

Image source: https://www.tanks-encyclopedia.com/coldwar/France/Panhard_AML.php

Brandt did interesting work with 60mm, and later 81mm gun-mortars. The US Coast Guard also used a dual .50/81mm mount on patrol boats that allowed firing down to nearly horizontal during the Vietnam era.

That was a US Navy design which was first intended for a new generation of post war PT Boats (PT 809, 810, 811 & 812).

 

[BB1984]

Brandt did interesting work with 60mm, and later 81mm gun-mortars. The US Coast Guard also used a dual .50/81mm mount on patrol boats that allowed firing down to nearly horizontal during the Vietnam era.

That was a US Navy design which was first intended for a new generation of post war PT Boats (PT 809, 810, 811 & 812).

Are you sure it was the .50/81mm combination? I knew US PT boats used both 60mm and 81mm mortars in WWII and an 81mm is listed as PT809 armament, but at least one source (Navypedia) specifically says it's the regular, infantry M29 mortar. I looked at a couple pictures of the PT809 too, and it's hard to tell but it looked to be just the mortar, not the combined mount. Armament listings for the PT809 seem to list 81mm, 20mm, and 40mm but no .50, so all this indicates just the mortar, though maybe it's not definitive, especially since PT boats were notorious for changing and eclectic weapons fits, or at least the wartime ones were.

I also dug up this article from the 1997, which details a Coast Guard development history for the 81/.50. It starts with a need for better illumination rounds (as I believe the PT boats did) and then progresses to the 81/.50 combined mount entering service in 1964-65 on Coast Guard boats.
http://www.berthdeck.com/Articles/81_50.pdf

 

[A Tentative Fleet Plan]

Brandt did interesting work with 60mm, and later 81mm gun-mortars. The US Coast Guard also used a dual .50/81mm mount on patrol boats that allowed firing down to nearly horizontal during the Vietnam era.

That was a US Navy design which was first intended for a new generation of post war PT Boats (PT 809, 810, 811 & 812).

Are you sure it was the .50/81mm combination? I knew US PT boats used both 60mm and 81mm mortars in WWII and an 81mm is listed as PT809 armament, but at least one source (Navypedia) specifically says it's the regular, infantry M29 mortar. I looked at a couple pictures of the PT809 too, and it's hard to tell but it looked to be just the mortar, not the combined mount. Armament listings for the PT809 seem to list 81mm, 20mm, and 40mm but no .50, so all this indicates just the mortar, though maybe it's not definitive, especially since PT boats were notorious for changing and eclectic weapons fits, or at least the wartime ones were.

I also dug up this article from the 1997, which details a Coast Guard development history for the 81/.50. It starts with a need for better illumination rounds (as I believe the PT boats did) and then progresses to the 81/.50 combined mount entering service in 1964-65 on Coast Guard boats.
http://www.berthdeck.com/Articles/81_50.pdf

Friedman's US Small Combatants states that the 81mm Mortar Mark 2 was developed for Post War PT Boats and first tested in 1951, but did not enter widespread service until the Vietnam war. The version with the piggyback 0.50 was the Mark 2 Mod 1.

There was also a postwar 60mm mortar mount Mark 4, which replaced the aft 0.50 mounting on some PBRs. A piggyback M60 machine gun could be added.